This invention relates, in general, to fluidized bed combustion and, in particular, to a new and useful pressurized fluidized bed combustor, which includes a reaction chamber having a multiplicity of vertically extending cooling tubes arranged therein and to an improved construction of the cooling tubes and a cluster arrangement of such cooling tubes.
Many types of fluidized bed combustors are known. In addition, combustors are known in which the fluidized bed combustor is operated at an elevated pressure and a fluid, such as compressed air, is employed for effecting the pressurization of the reaction chamber. It is known in such reactors to provide a bed of particulate matter including coal which may be blown into the reactor chamber, for example, by nozzles which also provide a combining of the coal with combustion air. Initial firing of such reactors is sometimes carried out by gas burners or by one or more oil burners in addition to coal fire burners. It is known to use such reactors for carrying out various drying, heating and heat transferring operations in which a fluid, such as air or water is usually employed to cool the fluidized bed and to transfer heat into the working fluid for other uses, such as for driving a turbine. Many types of reactor constructions are known which include cooling or heat exchanger tubes which are arranged either vertically or horizontally, both in the fluidized bed and above the fluidized bed. In many instances, the high temperatures prevalent in the bed lead to the clogging of the space between the heat exchanger tubes as well as deterioration or wearing out of the tubes so that they must be replaced or repaired. In the known construction, the tubes must usually be separately removed and replaced after the reactor is shut down.